In general, salt meters measure salinity by using a property in which electrical conductivity is changed according to an ion concentration of sodium chloride (NaCl) contained in foods. That is, a pair of electrodes may contact an object to be measured (hereinafter, referred to as a measurement object), and then a voltage may be applied into the pair of electrodes to measure an amount of flowing current, thereby obtaining salinity of the corresponding object.
To measure salinity, a power button may be pushed in a state where a salt meter is put inside a cooking container to contact a food, or a measurement button may be pushed when the power button is turned on to measure the salinity of the food. That is, the salt meter should be immersed into a measurement object for a predetermined time, and also, a separate switch should be manipulated to measure the salinity. In addition, since a switch that is necessarily provided for manipulating is an electrical device, the switch must be waterproofed.
For this, a salt meter 10, as shown in FIG. 1, includes a measurement part 12, a display part 13, and a manipulation part 14 on a main body 11 defining an outer appearance thereof. The manipulation part 14 according to the related art includes a button type switch 15 which is generally exposed to the outside and is manipulated through a push or touch operation. The switch 15 is mounted on a board 16 on which a predetermined circuit is printed. The switch 15 has one side passing through a hole and exposed to the outside of the main body 11. Also, a waterproof film 17 surrounds the switch 11 together with the main body 11. Thus, the salt meter may measure salinity or temperature within the measurement object.
The switch operable by the push or touch operation as described above may be easily manipulated. However, as the switch is incalculably and repeatedly touched to wear the waterproof film 17. As a result, the switch is used for a long time to make a hole in the waterproof film, thereby losing the waterproof function. Also, when a measurement apparatus is manufactured, a process of attaching the separate waterproof film 17 for protecting the switch 15 should be performed. Thus, the manufacturing process may be complicated, and also, manufacturing costs may be increased. Also, to apply a switching device into the measurement apparatus being gradually miniaturized, the switching device should be gradually miniaturized. Thus, the push or touch operation by a user may be trouble to limit the miniaturization.
To solve the above-described limitations, a salt or temperature measurement apparatus which is operated by using electrical conductivity without a separate touch operation by the user is being proposed. However, since a basic power source should be continuously supplied into the measurement apparatus using the electrical conductivity to detect a flow of current between electrodes, it may be very disadvantageous in power consumption.
Currently, vibration detection apparatuses using elasticity are proposed with the purpose of earthquake sensing or security. However, such a vibration detection apparatus may detect only simple vibration and also not be used as a switching device for ON/OFF operation.